The invention relates in general to couplings and in particular to a new and useful fitting for connecting circumferentially ribbed insulating tubes of plastic.
There are known fittings for connecting such insulating tubes intended to enclose electrical cables, which are equipped with a locking element which can be inserted in a recess in the wall of the tube receiving socket of the fitting and is provided with projections to be engaged with circumferential grooves of the insulating tube. For example, known is a U-shaped locking element which, upon introducing the insulating tube, is inserted through a wall recess to straddle the insulating tube and engage the circumferential grooves of the tube by its projections, while the resilient legs of the locking element engage behind webs by which the recess is interrupted and thus prevent the locking element from being unlocked without a tool. Aside from the fact that such a locking element extending over about 180.degree. of the circumference of the receiving socket is relatively complicated to manufacture, the interruption of the wall recess by webs for anchoring the element requires a relative extensive recess in the wall. Moreover, the manufacture, supply and handling of separate locking elements is undesirable.
The present invention is therefore directed to a fitting comprising a locking element fixed thereto and being particularly simple to manufacture and handle, while still being manually engageable into its effective position and prevented from being disengaged therefrom without a tool.
In accordance with the invention a fitting is provided which includes a cylindrical member having an opening at each end with one end advantageously being of a smaller diameter than the opposite end so as to form a ledge therebetween through which a sealing element such as a sealing sleeve or ring is placed. The fitting is used for connecting a tube which has circumferentially extending axially spaced ribs defining recesses between the ribs on its exterior surface. The tube is placed in the large diameter portion and abuts against the sealing ring and it is locked within the fitting by a locking lid which is positionable in a slot of the socket which overlies the exterior circumferential tube. The locking lid includes a portion which is connected to the socket and is flexible and holds the fitting at an acute angle in inoperative position above the surface of the socket. After insertion of the tube the locking lid is closed forcing an outer bevelled lip past the edge of the slot so that it underlies the interior of the socket. In this position the locking lid includes a projection which extends into a recess between the ribs of the tube so that it locks the tube in position.
The firm connection between the receiving socket and the locking lid particularly simplifies the handling of the locking element. Further, the socket may be designed as a polyhedral body, with the recess and the locking lid being provided in one of the plane faces thereof. In a particularly advantageous embodiment of the invention, the wall thickness of the rectangular locking lid is substantially equal to that of the receiving socket while the bending strip forming the hinge and the free end to be engaged below the edge of the recess have a reduced wall thickness, so that the lid when it is in an effective position is flush with the polyhedral face. Since a single, circumferentially relatively narrow recess is needed in the socket, the socket wall is not noticeably weakened. The axial length of the recess and thus of the working lid is advantageously such as to be able to provide, on the inside of the lid, two or three projections designed as cross ribs having edges comformable to the concavity of the socket and being spaced apart in accordance with the spacing of the ribs of the insulating tube to be inserted. It has been found particularly advantageous to provide the inwardly projecting, jutting portions of the lid in an arrangement such that in the effective position of the lid, they engage the ribs of the insulating tube to urge the tube inwardly, into the socket, against a sealing sleeve accommodated therein. The corresponding reacting force of the sealing sleeve then urges the free end of the lid reliably below the edge strip, whereby an unassisted disengagement of the lid from its effective position, for example due to shocks, vibrations, etc. is virtually prevented.
Accordingly it is an object of the invention to provide an improved fitting for connecting tubes which have circumferentially extending axially spaced ribs, which includes a locking lid which is connected to a socket member receiving the tube by a bending strip portion of the locking lid which orients the lid at an acute angle from the surface of the socket and permits the locking lid to be bent inwardly so that projections on the interior surface of the socket engage into the recesses of the tube and lock it in position.
A further object of the invention is to provide a fitting for connecting tubes which is simple in design, rugged in construction and economical to manufacture.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.